1. Field of the Invention
The invention relates to a method for briquetting metal chips and a briquetting press for carrying out the method.
2. Description of the Related Art
DEA-40 39 788 discloses briquetting presses that have at least one pressing ram disposed in a pressing sleeve to press metal chips in the form of briquettes. A stamper is used to feed the metal chips to a metering device disposed radially in relation to the pressing sleeve. The process flow is as follows:                advancing the stamper, filling and closing the pressing sleeve,        advancing the pressing ram and feeding the metal chips into the pressing section of the pressing sleeve,        applying pressure to the metal chips with at least one pressing ram until a final pressure Pmax or a required pressure Preq is attained,        optionally, retracting a second pressing ram and expelling the completed pressed article as a briquette using the first pressing ram, and        retracting the first pressing ram and, optionally, advancing the second pressing ram into the initial position.        
The aforedescribed, optionally double-acting, briquetting presses, unlike conventional briquetting presses, produce a pressed article with a particularly high densification approximating the intrinsic density of the metal, and also have a high throughput, thereby optimally achieving both a high density and a high efficiency. In contrast to single-sided presses, significantly longer briquettes can be produced, because the stroke lengths, in order to be manageable, have to stay within practical limits, as determined by the machine tool and the manufacturing environment.
EP-A-0 367 859 also describes a method and a briquetting press for making briquettes having dimensional stability from pressed material in the form of chips, fiber, dust, and lamellar material. The material to be pressed is hereby fed to a precompacting plunger and precompacted in a receiving chamber and thereafter further compacted in a forming box by a press plunger which moves perpendicular to the precompacting plunger. According to this invention, by exactly determining the end position of the press plunger and the precompacting plunger, respectively, variations in the material to be pressed can be almost entirely eliminated, so that the intended power of the press can be utilized with a high efficiency.
However, the results from these technical teachings can not be applied to axially-aligned, double-acting briquetting presses.
U.S. Pat. No. 5,326,511 also teaches a solution similar to that of the previous reference. However, even when taking into account all the features of this type of presses which operate with a precompacting plunger and a press plunger in mutually perpendicularly disposition, the prior art presses do not suggest an obvious solution that can be adapted to pressing rams operating in opposing directions in a pressing sleeve, since this arrangement represents a completely different type of press with an entirely different operating characteristic.
Indeed, a double-acting briquetting press with pressing rams operating in a pressing sleeve cannot easily produce pressed articles in the form of briquettes with a workable and acceptable length and also a small manufacturing tolerance. Disadvantageously, the maximum possible fill volume in the pressing sleeve over the length of the briquette can hence not be fully utilized even if maximum pressing power is applied.